In a general packet radio service (General Packet Radio Service, GPRS for short) network, a terminal entity/mobile terminal (Terminal Entity/Mobile Terminal, TE/MT for short), that is, an MS, through a base station subsystem (Base Station Subsystem, BSS for short), can access a packet data network (Packet Data Network, PDN for short) through serving GPRS supporting nodes (Serving GPRS Supporting Node, SGSN for short) of multiple operators. This feature may be called a multi-operator core network (Multi-Operator Core Network, MOCN for short). The feature of the BSS may be called support of MOCN.
When the MS requests for accessing a network through the BSS, because the BSS cannot know which operator's SGSN can serve the MS, the BSS tries to send to each SGSN one by one an access request message from the MS. If an SGSN that receives the access request message judges that the MS cannot perform access, a reject cause and an access request reject message that includes the reject cause are returned to the BSS; and if the SGSN that receives the access request message judges that the MS can perform access, an access procedure of the MS is performed. When the BSS receives a reject cause and an access request reject message that includes the reject cause, where the reject cause and the access request reject message are sent by one SGSN, the BSS needs to redirect the access request message of the MS to another SGSN. Each message exchanged between the SGSN and the MS corresponds to one logical link control (Logical Link Control, LLC for short) parameter, for example, a sequence number used by an LLC layer. The MS can acquire the message and interact with the SGSN normally only when an LLC parameter corresponding to a message that is sent by the SGSN to the MS is consistent with an expected LLC parameter of the MS.
In the prior art, after the BSS redirects the access request message of the MS to another SGSN, the another SGSN needs to interact (for example, authenticate) with the MS. However, an LLC parameter corresponding to a message that is sent by the another SGSN to the MS may be inconsistent with an expected LLC parameter of the MS (that is, an LLC parameter expected by the MS according to an LLC parameter corresponding to a last message that is exchanged with a previous SGSN), so that the MS discards the message that is sent by the another SGSN to the MS, thereby affecting normal interaction between the another SGSN and the MS.